Solid vehicle tire



Oct. I1, 1927. 1,645,089

NNNNNN OR Patented Oct. 11, 1927.

UNITED STATES PATENT OFFICE.

RICHARD S. BURDETTE, OF AKRON, OHIO, ASSIGNOR T THE GOODYEAR TIRE 66 RUB- BER COMIPANY, OFAKRON, OHIO, A CORPORATION 0F OHIO.

SOLID VEHICLE TIRE.

Application 1ed January^ My invention relates to rubber f vehicle tires and it particularly contemplates a modification of conventional rubber vehicle tires that greatly prolongs the operating life 5 of the tires to which it is applied.

Solid rubber vehicle tires previously have been made in a great many different forms but all of such tires, as have come Within my observation, have been subject to premature failure under test and in service,

when subjected to o verload, because of socalled under-cutting. By the term undercutting I refer to the rupture that occurs in the body of solid rubber tires, usually extending from the surface of the tire adjacent the base band into the body of the tire, in the zone of greatest shear stress intensit-y. Tires in ordinary commercial use that are subjected to any degree of overloading, generally fail by reason of such undercutting, which eventually extends very deeply into the bodyof the tire and, by reason of the continuous frictional engagement of the ruptured parts, the condition aggravates very rapidly after the rupture is once started, eventually causing premature and ultimately complete failure of the tire.

My invention resides in so forming the tire body as to provide means adapted to effectively distribute the shearing stresses developed in conventional tires along the line of the side Wall thatl is subjected to the greatest intensity of shear when the tire is under load.

By distributing the shearing stress, and thus reducing its intensity, I delay, and in many instances prevent, the initial ru ture ofk `the side wall of the tire because o undercutting from overload and I thereby greatly e@ prolong the life of the tire.

Failure from undercutting usually appears fiist as a mere line or sli ht Wrinkle extending around the side of t e tire. It then becomes a slight cut extending pare5 tially or completely around one or both sides of the tire and thereafter it rapidly deepens into the tire bod until the tire is no longer lit for service. Agfter undercutting has once started, failure of the tire therefrom quickly results. As previously stated, the rubbing of the sides of the open cut severely aggravates the destructive conditions to a point Where the tire is no longer fit for service,

although frequently only a small portion of 14, 1925. Serial No. 2,291.

the cushion body that is available for Wear is Worn away.

In accordance with my invention, I provide means for distributing the shear stresses over a Wider zone at the surface of the tire and thereby prevent or greatly delay the start of undercutting. This is accomplished by modifying the' side-Wall of the tire in the zone of greatest stress intensity in various Ways, all of Which apparently serve to distribute the stresses to a suiicient degree to del-ay initial undercutting and thereby greatly prolong the life of the tire. vIn certain forms of my inventionI employ a illet or bead of unconfined rubber that is positioned directly over the zone of greatest shear stress intensity. This distributes the stress over a much wider zone of the surface of the tire ,and thereby reduces the shear intensity in suiicient amount to prevent or at least materially delay rupture of the tire body from this cause.

In other applications of my invention, I

insert a fillet of rubber, or of other material having a modulus of elasticity differing from that of the tire body, in the zone of undercutting of the tire to thereby absorb and distribute the stresses over a greater area of the side ofthe tire than in conventional forms of tires to which the invention may be applied.' In other forms of the invention, I provide grooves' in thesides of the tire directly over the zone of greatest shearing stress intensity. The rounded bottom and side walls of such groove .appear to distribute the shear stresses over a greater area and to thereby prevent the premature rupture of the tir body.

Each of the figures of the accompanying drawings shows a transverse sectional view of a portion of a vehicle tire illustratin -di'erent forms of my invention, as applic to different tire bodies.

Referring particularly to Figure 1 of the accompanying drawings, the cushion tire there shown comprises a base band l, upon Which a cushion tire body 2a is permanently vulcanized. A test of tires of conventional form indicates that the maximum shear stresses occur substantially in the direction and position ofl the broken line 3 in tires of this general shape. After determining the position of the line 3 of greatest stress intensity, either by test or by calculation,

ll so construct the mold for the tire as to provide a bead or fillet l of unconfined rubber on the surface of thetire directly overlying the line of the side wall where the undercutting would naturally start. T have also found in tires of the four inch class, that the bead or fillet 4 should ordinarily be positioned about one-eighth of an inch above the base band. This is found to be true where the cushion body 2a is secured to the base band 1a by means of layers of hard rubber 5 and 6 that are customarily used in tires for establishing a secure union between the base band and the cushion body.

I have, also, found that when the hard rubber securing layers 5 and 6 are omitted, and where the cushion body 2b issecured directly to the base band 1b without such intervening layers, the Zone of greatest stress intensity is positioned relatively closer to the flanges or securing face of the base band 1". ln such tires it emerges substantially along a line 7 of the confining flange of the tire, as shown in broken line in Figure 2. By introducing a fillet 8 of unconfined rubberat this point of the tire body 2b, I have found that very satisfactory results are obtained. T provide an oblique flange that supports the outer edges of the base of the tire body and also that provides the fillet 8 of unconfined rubber that operates to distribute the shearing stresses over a greater zone of the surface of the tire. This may readily be accomlished b chamfering the corner 9 of the Ease ban This fillet 8 of unconlined rubber operates under load in substantially the same manner as the fillet 4 of the tire shown in the preceding figure.

Figure 3 shows an additional modification of my invention in which the base band l" is cut away, as indicated at 10, to provide space for a fillet 11 of unconfined rubber overlying the zone of greatest shear intensity. The difference between this form of tire and that Shown in the preceding figure resides in the slight shoulder 12 of the tire of lFigure 2 that is shown as extending above the base band whereas, in Figure 3 this portion of a tire lood is dispensed with and the side wall of the ody portion 2c is made to curve' uniformly to the chamfered surface 10.

In Figure 4 is illustrated an additional slightly different form of fillet that overlies the zone of greatest stress intensity and that substantially forms a continuation of the portion of the cushion body 2d adjacent the ase band 1", which confines a portion ofthe v tire body between the upstanding flanges 15.

It will be noted that, in each of the recedin Figures 1 to 4, inclusive, the ase band as upstanding ed e portions. My invention may also inclu e a fillet of unconined rubber 16 that is formed along the inner edge portions of a cushion body 2 that neaaeee is mounted on a substantially flat base band 1", as illustrated in Figure 5.

Figure 6 also shows a portion of a tire of substantially the form illustrated in Figure 5, in which the fillet of unconfined rubber Substantially forms a bead 17 along the outer edge of the cushion body 2k of the tire at the point of Contact with the base band 1k.

In addition to the above methods of distributing the shear intensity by forming a fillet on the outside of the tire body, li may insert a fillet of a material having a different modulus of elasticity within the body of the tire directly ove-r the zone of greatest shear intensity. This construction is shown in Figure 7 of the drawings, which shows a fillet l18 adjacent the base band 1f, that is either of harder or softer rubber compound than the remainder of the tire body 2f. Such filet is inserted within the tire body 2f over the normal undercut line. The material thus inserted prevents the concentration of the shear'stresses along a relatively narrow zone of the surface of the tire body 2f and thereby prevents undercutting.

I have also found that a strip of fabric 19 lor other tough vmaterial may be inserted in the tire body 2g over the zone of greatest shear intensity, as illustrated in Figure 9v Such construction will accomplish the result 'heretofore outlined: namely, distribute the shear stresses at the surface of the tire over a greater zone and thereby prevent premature undercutting adjacent. the base band 1S` In addition to the above methods of distributing the shear stresses over larger areaof the surface of the tire. l may form a y groove around the edge of the ti-re body il along the line of normal undercutting adja- 'cent the base band. Such construction func- -serve to illustrate various applications thereof that may beused with different forms of tires and that may be applied to'tires that have previouslylbeen molded in conventional form. For instance, the application of the fillet shown in Figures l to 6, inclusive, depends primarily upon a simple and inexpensive modification of the tire mold to rovide the necessary molding groove for the llet of unconfined rubber or upon the insertion of material overlying the line of undercut that has a different modulus of elasticity from that of the body of the tire. In fact, I have illustrated a method of distributing the shear intensity by cutting a circumferential groove in the tire side wall adjacent the base 'band llli at the 'point where undercutting usuallyl aeeaoee and prolonge the life of tires that have already been molded, although it has been found to be not so effective as certain of the other' suggested methods. rlhe form of tire shown in Figure) should not, however, be

confined to tires that have first been molded.

panying drawings, is formed on such tires,y

then the life of the tire is materially prolonged beyond the period of the normal life of corresponding tires having no such fillet formed thereon.

lThis may be explained by the fact that the base bands are inextensible and that they prevent any ow of the'rubber thatis securely vulcanized thereto. When load is applied to the tread of the tire, the body of the tire is deformed and the rubber, being substantially incompressible, flows outward ly at the sides of the tire. 'lhe zone of greatest stress intensity therefore occurs between the cushion body that is squeezed laterally and the portion of the body of the tire that is prevented from flowing by its union with the base band.

lt is therefore apparent that, if a bead or fillet of unconned rubber is provided at the zone of greatest shear intensity, this bead or fillet will distribute the stresses appearing in the surface portion of the tire over such a zone as to bring the stress intensity of that zone within the limit of elasticity of the rubber, which thereby absorbs the shear without rupture and prevents or greatly delays the initial undercutting of the tire.

It has beenfound in service that tires,

constructed in accordance with the invention shown in Figure l, very often fail ultimately through the breaking away of the bead or the actual separation of the bead t from the side wall of the tire. After the bead is separated from the tire wall, by reason of the ultimate fatigue and rupture of the material of the bead from the normal surface material of the tire, destructive undercutting develops in the usual way and extends back into the tire along the hne 3.

Although l have described several illustrative forms of the application of my ins1 vention to vehicle tires, il have not attempted to show every conceivable modification thereof, but have selected representative applications that are believed to show the method of applying the invention to the design of rubber tires and particularly tires of conventional form that are alread built. l therefore desire that l shall not e confined to the particular form of invention appearing in the accompanying drawings, but that l may be granted protection on all such modifications of the suggested solutions as may come within the spint and scope of the accompanying disclosure and the appended claim.

What l claim is:

A rubber vehicle tire comprisin a tread portion of substantially trapezoi al crosssection vulcanized to a metallic base band disposed along the inner periphery thereof, an a protuberance of resilient material between the side-edge of the base band and the side-wall of the tread portion, so disposed as to form a perceptible interruption of the curvature of the tread portion adjacent the base band and to distribute stresses that tend to cause the separation of the tread portion and the base band when the tire is under load. y l

lin witness whereof, l have hereunto signed/my name.

RICHARD S. BDETTE. 

